package pers.darren.encrypt.rsa;

import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

import org.apache.commons.codec.binary.Base64;

public class RSAEncrypt {
	private static Map<Integer, String> keyMap = new HashMap<>(); // 用于封装随机产生的公钥与私钥

	public static void main(final String[] args) throws Exception {
		// 生成公钥和私钥
		genKeyPair();
		// 加密字符串
		final String message = "my password";
		System.out.println("随机生成的公钥为:" + keyMap.get(0));
		System.out.println("随机生成的私钥为:" + keyMap.get(1));
		final String messageEn = encrypt(message, keyMap.get(0));
		System.out.println(message + "加密后的字符串为:" + messageEn);
		final String messageDe = decrypt(messageEn, keyMap.get(1));
		System.out.println("还原后的字符串为:" + messageDe);
	}

	/**
	 * 随机生成密钥对
	 *
	 * @throws NoSuchAlgorithmException
	 */
	public static void genKeyPair() throws NoSuchAlgorithmException {
		// KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
		final KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
		// 初始化密钥对生成器，密钥大小为96-1024位
		keyPairGen.initialize(1024, new SecureRandom());
		// 生成一个密钥对，保存在keyPair中
		final KeyPair keyPair = keyPairGen.generateKeyPair();
		final RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); // 得到私钥
		final RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); // 得到公钥
		final String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
		// 得到私钥字符串
		final String privateKeyString = new String(Base64.encodeBase64(privateKey.getEncoded()));
		// 将公钥和私钥保存到Map
		keyMap.put(0, publicKeyString); // 0表示公钥
		keyMap.put(1, privateKeyString); // 1表示私钥
	}

	/**
	 * RSA公钥加密
	 *
	 * @param str       加密字符串
	 * @param publicKey 公钥
	 * @return 密文
	 * @throws Exception 加密过程中的异常信息
	 */
	public static String encrypt(final String str, final String publicKey) throws Exception {
		// base64编码的公钥
		final byte[] decoded = Base64.decodeBase64(publicKey);
		final RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")
				.generatePublic(new X509EncodedKeySpec(decoded));
		// RSA加密
		final Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, pubKey);
		final String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
		return outStr;
	}

	/**
	 * RSA私钥解密
	 *
	 * @param str        加密字符串
	 * @param privateKey 私钥
	 * @return 铭文
	 * @throws Exception 解密过程中的异常信息
	 */
	public static String decrypt(final String str, final String privateKey) throws Exception {
		// 64位解码加密后的字符串
		final byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
		// base64编码的私钥
		final byte[] decoded = Base64.decodeBase64(privateKey);
		final RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")
				.generatePrivate(new PKCS8EncodedKeySpec(decoded));
		System.out.println("私钥N值：" + priKey.getModulus().toString());
		System.out.println("私钥E值：" + priKey.getPrivateExponent().toString());
		// RSA解密
		final Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, priKey);
		final String outStr = new String(cipher.doFinal(inputByte));
		return outStr;
	}

}